This invention relates to a tape loading device for use in a rotary head-type magnetic conversion apparatus (e.g. VTR), in which a tape-like recording medium (hereinafter referred to as "tape") is taken out from a tape reel, and is wound on a rotary drum having magnetic heads mounted thereon, and magnetic information is recorded on and/or reproduced from the tape by the magnetic heads, and the tape wound on the rotary drum is taken up by another reel. The invention relates more particularly to a tape loading device for use in a helical scan-type magnetic conversion apparatus in which the tape is wound on the rotary drum in an inclined manner.
2. Description of Related Art
A video tape recorder including a rotary drum with magnetic heads mounted thereon, and a tape cassette containing two tape reels (i.e., a supply reel and a take-up reel), or a recording/reproducing unit of the helical scan type for use with a tape cartridge containing a single tape reel, need to be provided with a tape loading device by which a tape is taken out from the tape cassette or the tape cartridge and is wound on the rotary drum over a predetermined angle.
There is known one such tape loading device for such units, in which a tape is taken out by a tape guide movable in an inclined plane and is wound on a rotary drum from one side thereof.
For example, there is known a tape loading device of the type in which an inclined, disk-like loading ring, having a plurality of tape guides mounted thereon, is angularly movably disposed around a rotary drum, and the loading ring is angularly moved to cause the tape to be taken out and wound on the rotary drum by the tape guides. In such a tape loading device, either a tape travel path from a supply tape reel to the rotary drum or a tape travel path from the rotary drum to a take-up tape reel is in the same horizontal plane as the tape reels, so that the height and the inclination will not be varied. In the other tape travel path, the tape, helically or spirally wound on the rotary drum and then disengaged therefrom, is inclined, and therefore this travel path has two tape travel planes, that is, the inclined tape travel plane parallel to the loading ring, and the horizontal tape travel plane which is the same as that of the tape reel. The tape is wound on an inclined post provided at the boundary between the two tape travel planes, thereby changing the tape travel plane without twisting the tape. In the case of such a tape loading device having a loading ring, in order to avoid interference of the loading ring with the tape travel path, the tape is wound on the rotary drum downwardly from the horizontal plane. Therefore, the plane of inclination of the loading ring is also downward from the horizontal plane.
In the above tape loading device, by a tape take-out means movable in a horizontal plane, the tape is first taken out from the tape cassette or the tape cartridge in the same plane as that of the tape reels to thereby form a predetermined semi-loaded condition. Then, by rotating the loading ring, the tape is engaged by the leading tape guide on the loading ring, and the tape is spirally wound on the rotary drum over a predetermined angle, for example, from the take-up tape reel side. Thus, the tape is taken out by the tape guide moving in the inclined plane in which the loading ring is mounted, and is wound on the rotary drum from one side thereof. This type is called a U-loading system because of the configuration of the tape travel system in its loading-completed condition.
In such a tape loading device, the loading ring, as well as the tape guides on the loading ring, is designed in accordance with the inclination of the tape travel plane in the loading-completed condition. Therefore, during the loading operation, the tape is liable to be twisted, so that the tape may be damaged. For example, the upper and lower edges of the tape are expanded and corrugated because of the difference in tension between the upper and lower tape edges.
To prevent such damage, there is proposed in Japanese Patent Unexamined Publication No. 64-10455 a tape loading device having a mechanism by which an inclined post is rotated about a predetermined point in accordance with angular movement of a loading ring so that the angle of winding of a tape on the inclined post can always be kept to the angle of winding on the inclined post in a loading-completed condition.
There is also proposed in Japanese Patent Unexamined Publication Nos. 60-5454 and 4-114348 a construction having a mechanism by which the inclination of a leading tape guide on a loading ring is changed to a vertical disposition only when the leading tape guide begins to contact a tape.
Twisting of the tape, which is a problem with the prior art techniques, is caused by two factors, that is, (1) the angle of winding of the tape on the inclined post for changing the tape travel path from the horizontal tape reel plane to the surface of the tape guide on the inclined loading ring is varied during the loading operation, and (2) the tape is twisted between the leading tape guide on the loading ring and the rotary drum because the angle of winding of the tape on the rotary drum is varied during the loading operation.
The tape loading device disclosed in the above Japanese Patent Unexamined Publication No. 64-10455 can overcome the tape twisting factor (1), but can not overcome the factor (2) by which the tape is twisted between the rotary drum and the leading tape guide, so that the tape damage caused by caused by the leading tape guide during the loading operation can not be effectively prevented.
Moreover, when the loading operation begins, the tape, disposed in the horizontal tape reel plane in a semi-loaded condition, is taken out by the leading tape guide on the inclined loading ring. However, since the leading tape guide is mounted on the inclined flat surface slanting downwardly, the leading tape guide is disposed at a level or height lower than the tape, and is kept inclined at a position where the leading tape guide begins to contact the tape. In this condition, each time the loading operation is effected, a flange formed at an upper end of the leading tape guide engages the surface of the tape, and this causes tape damage.
In this respect, the above Japanese Patent Unexamined Publication Nos. 60-5454 and 4-114348 disclose constructions in which the tape can be kept in a proper posture at the position where the leading tape guide begins to contact the tape and also when the loading operation is completed, but there has been encountered a problem that the tape can not be kept in a sufficiently proper posture during the loading operation.